1. Field of the Invention
The present invention relates to a gas laser and particularly relates to a multicomponent gas purification, in which a gas medium such as a laser gas medium or the like is used while being circulated and purified.
2. Description of the Related Art
Although a description will be set forth, by way of example, of the case where the present invention is applied to a KrF excimer laser, the invention is not limited to such KrF excimer laser. For example, the invention may be applied to an ArF excimer laser, purification of multicomponent gases, and so on.
A KrF excimer laser is operated in a manner so that a mixture of gas of about 95-99% of Ne, about 1-5% of Kr and about 0.1-0.5% of F.sub.2 is contained as a laser gas medium in a laser tube, which is made of metal, glass, plastics, ceramics or the like, and has mirrors disposed at the opposite ends of the laser tube, and light emission is caused in the laser gas medium through electric discharge to thereby cause resonance.
In general, fluorine gas is strong in reactivity and, in particular, fluorine gas excited by electric discharge or other excitation means is so strong in reactivity that a reaction between the florine gas and constituent materials of the laser vessel is caused by the electric discharge. This can generate a level of impurities in the laser gas which causes the laser output from the KrF excimer laser to decrease as the number of discharge pulses increases due to the presence of these impurities.